Filter

ABSTRACT

A filter element is longitudinally formed in a frusto-conical shape The filter element has a plurality of radially extending members that form a propeller shaped cross-section, and a propeller-shaped moulded bottom that enhances dust fall from the exterior. A frusto-conically-shaped inner cage facilitates the shape of the filter element.

FIELD OF THE INVENTION

The present invention relates to filters used in air filtrationgenerally and is more specifically related to pulse-jet filter elementsand filter-cage assemblies, and to cartridge filters, of the typetypically used in industrial applications.

BACKGROUND OF THE INVENTION

Filter elements in use have cylindrical filter bags, mounted ontocylindrical wire cages, which are installed by means of snap-ringfittings in the housing. Air is drawn through the filter bags during thefiltration process. In pulse-jet filter applications, the air flowdirection is reversed during the cleaning cycle.

The filter bags are closed on the bottom and open on the top. The dustladen air is drawn through the filter bag from an exterior of the filterbag, and the dust particles are retained on the surface of the filterbag. The air-to-cloth ratio, dust particle size, electrostaticproperties of dust and filter cloth, can velocity, dust retention andcake-release of a given filter material and the filtration surfacetexture determine the efficiency of a filter. Pulse-jet filter bags arelimited by the length and circumference of the filter bags and the canvelocity due to the small open space between the circular filter bagsand bag housing. Improving efficiency by increasing the size of thefilter housing, or increasing the number of filter bags, is expensiveand is often impractical. The circular, sewed-on bottoms often protrudebeyond the sides of the filter elements and become obstacles that catchand collect dust, which later impedes dust release in the cleaningcycle, and creates a negative impact on the can velocity at the bottomof the filter elements.

Similarly, cartridge filters have the disadvantage of being limited intemperature resistance and in length, which typically may not exceed twometers. High differential pressure causes the pleats to concave at thetips of the pleats, thereby reducing the effective filter area at thispoint. In addition, dust and other undesirable particles build up on theoutside between the pleats and, in some cases, completely clog thecartridge filter. The extruding rim of the bottom plate of the cartridgefilter is frequently an obstacle that catches and retains dust,preventing the collected dust from falling down into the hopper.

SUMMARY OF THE INVENTION

The filter has radially extending fingers or rays that yield a filterbag having a propeller-shaped cross section. The present inventionsignificantly increases the filtration surface while using the samenumber of filter elements at the same gas volume, and also using thesame bag diameter and bag length of conventional pulse-jet filter bags.Additionally, the structure of the invention reduces the air to clothratio, can velocity and differential pressures, which leads tosignificant efficiency gains with respect to emission values and energyconsumption.

Radially extending portions of the filter elements lend a propellershape to the device of the invention. The sides of the bag are formed toallow an easy collection of dust. and the propeller-shaped bottom of thebag has no obstacles that accumulate falling dust, thus enhancingdust-cake release during the cleaning cycle. By substituting normalpulse-jet filter elements with frusto-conical, propeller-shaped mouldedbottom filter elements in a jet-filter bag-housing, this inventionsubstantially increases the filter capacity of the bag housing, whilesimultaneously significantly reducing energy consumption and operatingcosts. The number of filter elements, as well as space needed for thenew filter housing, is substantially reduced.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a 6-ray frusto-conical propeller-shapedembodiment of the fabric filter used in a filtration process.

FIGS. 2, 3, 4, and 5 are cross-sectional views of different embodimentsof frusto-conical propeller-shaped bottoms projected into the top opencircle of the corresponding filter element (cell plate and gasketingsize), demonstrating the frusto-conical form of each of thesefrusto-conical, propeller-shaped filter bags.

FIG. 4 a demonstrates additional open space gained between the bottomsof frusto-conical filter elements in comparison to using cylindricalfilter elements.

FIG. 6 is a cross-sectional view of the basic support element beforeforming to a required size (diameter of cage), with standardized ringand 8 standardized rays with eyes.

FIG. 7 is a cross-sectional view of the ring and one ray with eye ofFIG. 6 bent 90° to the diameter size of the frusto-conicalpropeller-shaped support cage.

FIG. 8 is a plan view of two typical, but dimensionally different,frusto-conical propeller-shaped filter elements with accompanying innerpropeller-shaped support cages.

FIG. 9 is a plan view of a frusto-conical propeller-shaped filterelement with an integrated flange to replace a typical pleated cartridgefilter element.

FIG. 10 is a perspective view of a propeller-shaped moulded bottom orboot.

FIG. 11 is a side view of the top of a 8-ray frusto-conicalpropeller-shaped filter element without pleats and with ring cuff.

FIG. 12 is a side view of the top of a 6-ray frusto-conicalpropeller-shaped filter element with box pleats and snap-band cuff.

FIG. 13 is a side view of the cylindrical top part of a 8-rayfrusto-conical propeller-shaped filter element with a ring cuff, whichis preferred when using interior venturis.

FIG. 14 is a side view of the top part of a 8-ray frusto-conicalpropeller-shaped filter element, whereby a cylindrical cuff with asnap-band is sewed onto a propeller-shaped filter element with boxpleats, which is preferred when using interior venturis.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a perspective view of a 6-ray frusto-conical propeller-shapedembodiment of filter bag 10. The filter bag is shown as used during afiltration process under negative differential pressure. A horizontal,circular band 12 may surround the filter bag. The filter bag 10 iscomprised of filter cloth 11 which has a circumference that ismaterially larger than the circumference of the circular band 12. Thecircular band is preferred to be circumferentially attached in regularintervals by fasteners such as staples 13 or seams, or other techniquesto the filter fabric 11, thereby holding the filter bag 10 permanentlyin a propeller shape 40. This design allows the filter cloth 11 known inthe art, such as needled felt, non-woven material, woven material,warp-knitted, circular knitted, micro-filament or micro-fiber fabric,fiberglass and/or woven metal or monofilament filter material to formover the longitudinal wire pairs 31 of the inner cage 30 into apropeller shape during filtration, and hold this position during thereversal of air or gas flow during the cleaning cycle.

In a preferred embodiment, the propeller-shaped filter bag 10 is placedover a frusto-conical propeller-shaped support cage 30. This supportcage is preferred to be formed by supports 32 and pairs of laterallyoffset frusto-conical longitudinal wires 31 that form the frusto-conicalcage. FIG. 8. The longitudinally, evenly spaced supports 32, as shown inthe embodiment of FIG. 6, are comprised of a ring 33 withradially-outwardly-in-equal-distance-arranged rays with eyes 34, whichare bent to the proper diameter needed (FIG. 7), and may be connected byblind rivets 35 to the washers 36 holding together each pair of wires 31and so forming a ray 14 of the frusto-conical propeller pattern. Thefilter bag as shown ends in a moulded propeller-shaped bottom 15 (FIG.10), and may be installed by means of a ring 16, snap-band 17 or otherfixture integrated in a top portion of the assembly, as shown in FIGS.11-14.

FIG. 2 shows a propeller-shaped metal end piece 37 of a 4-ray cageembodiment of the invention. This will support, for example, a 110/95 mm frusto-conical propeller shaped bag 10 rendering, for example, about54% more filtration area than a 110 mm  pulse-jet filter bag of thesame length as previously known.

FIG. 3 shows an embodiment of the invention having a propeller-shapedmetal end piece 37 of a 6-ray cage. A 140/115 mm  frusto-conicalpropeller-shaped bag 10 of this embodiment offers about 64% morefiltration area in comparison to a 140mm  pulse-jet filter bag 44 ofequal length as previously known.

FIG. 4 shows an embodiment of the invention having a propeller-shapedmetal end piece 37 of a 8-ray cage. A 150/130 mm  frusto-conicalpropeller-shaped bag 10 of this embodiment renders 100% more filtrationsurface than a 150 mm  pulse-jet filter bag 44 of the same length aspreviously known.

FIG. 4 a shows a foot print demonstrating the additional open space 41gained when replacing 150 mm  pulse-jet filter bags previously knownwith 150/130 mm  frusto-conical propeller-shaped filter bags 10 havingmoulded propeller-shaped bottoms 15. FIG. 4. In this embodiment, thegain of additional open space between the bags is 35%, reducing the canvelocity by the same percentage, with a constant gas volume. By cuttingthe air to cloth ratio in half, the differential pressure will bereduced by about 40% or more. A mean diameter 42 of 100 mm  inconnection with the propeller form 40 significantly reduces the particlemigration from row to row of filters during the cleaning cycle. As aresult, cleaning pressure can be lowered, for example, to as low as 2.2bar, which will lead to higher filtration efficiency, and reduceparticle-migration after the pulse-jet cleaning cycle. Energy savings ofas much as 50% or more yields substantial economic gains, lesswear-and-tear on the filter elements and, therefore, extended life-spanof the filter elements.

FIG. 5 shows a propeller-shaped metal end piece 37 of a 9-ray cage for a170/145 mm  frusto-conical propeller-shaped filter bag 10 rendering100% more filtration area in comparison to a 170 mm  pulse-jet filterbag 44 of equal length.

FIG. 6 shows a support element 32 comprised of a ring 33 with 8 radiallyoutwardly and equally-spaced-apart rays with eyelets 34. For all knownbag diameters 44 of this embodiment, the same ring 33 and the same rayswith eyelets 34 can be used, which will be bent to the required diameteras shown in FIG. 7.

FIG. 7 discloses an embodiment comprising pairs of laterally offset andfrusto-conical longitudinal wires 31 that are connected by means ofblind rivets 35. The wire pairs are separately made to length by spotwelding special washers 36 in-equal-distance to both wires.

FIG. 8 shows an embodiment of two typical frusto-conicalpropeller-shaped filter elements 10 without box-pleats 18 at the top,and with moulded propeller-shaped bottoms 15. One filter element is a4-ray version with snap band cuff 17 and one filter element is an 8-rayversion with ring cuff 16. The corresponding frusto-conicalpropeller-shaped support cage 30 is shown beside its filter element.

FIG. 9 shows an embodiment of a frusto-conical propeller-shapedcartridge filter element 20 without box-pleats 18 at the top, with topring cuff 16 and with a moulded propeller-shaped bottom 15 mounted on anexchangeable frusto-conical, propeller-shaped support cage 30 with a topflange 38. The much higher air to cloth ratio of this cartridge filterelement will more than compensate for the smaller filtration area incomparison to a star-like pleated cartridge filter. The mouldedpropeller-shaped bottom 15 and the drop-off sides 43 reduce the canvelocity, improve the cleaning efficiency, and will not allow the filterelement to clog up as is so often experienced with conventional pleatedcartridges with agglomerating dust, e.g. wet paper dust, and dust fromplasma welding or laser cutting.

FIG. 10 shows an embodiment of a typical 8-ray moulded propeller shapedbottom or boot 15 with open drop-off sides 43. This boot can beeconomically produced and attached to the main filter body, such as bysewing a horizontal seam 21. FIG. 9.

FIG. 11 shows a preferred version of a top without pleats 18, and havinga ring cuff 16.

FIG. 12 shows another version of a top with box pleats 19 and snap-bandcuff 17.

FIG. 13 shows an embodiment showing cylindrical top with ring cuff 16and inner overlap seams 22 as recommended for interior venturis.

FIG. 14 shows a cylindrical top with snap-band cuff 17 sewed with ahorizontal seam 21 onto a propeller-shaped filter corpus with box pleats19, which is preferred for interior venturis.

In the preferred embodiment shown in FIGS. 9 and 11, the filtercartridge and filter bag are without pleats at the top and have amoulded bottom. Both filter elements are open at the top and closed onthe bottom. The bottom piece of the frusto-conical propeller-shapedfabric filter is moulded in the exactly required radially extendingpropeller form and may be secured by fasteners such as metal clamps orstaples.

Polyurethane, silicone or other mouldable material may be used to formthe moulded bottom of the filter bags. The very top of a preferredfilter bag is not propeller-shaped, but is cylindrical. Snap-band ringswith double-beaded gasketing, felt strips, rings or other conventionalinstallation methods may be employed for mounting the filter bags. Theopen top can therefore be made to fit any standard cell plate andgasketing size.

The filter media may be chosen from many materials used for industrialdust filtration, and may be needled felt, non-woven, woven material,warp-knitted, circular knitted fabric also out of micro-filament yarnand fibers, fiberglass and/or metal-fabrics, and others. The length anddiameter of the filter bag is variable in accordance with the needs inline of the filter housing dimensions. A preferred filter element of theinvention comprises filter media which can withstand temperatures up to280° C.

Interior venturis or special types of filter material (e.g. glass,woven, light-weight-spun-bond material) may make it desirable to deviatefrom the preferred pleat-free open top form and to use a box-pleatdesign sewed onto a tubular top FIG. 14 or an inner overlap-seam design,forming a tubular top. FIG. 13.

Bands on the exterior of the filter bag may be used to give the filterelement the multi-propeller-blade shape, and also prevent the filter bagfrom expanding too much during the pulse-jet cleaning cycle. The bandsare placed horizontally around the filter bag at calculated intervalsalong the length of the bag. The smaller outer-circumference of thefilter element is created by matching marks on the band toproportionally-greater-distanced marked points on the bags. These marksare then joined together by sewing, stapling, or other techniques.

The filter bag must have an inside support, which may be a cage. To meetthe needs of the individual application, this cage is preferred to beconstructed of rigid materials such as steel or stainless steel, wherebyall steel parts can be treated or coated as required. The cage may have,for each propeller-blade, a pair of wires forming a frusto-conical shapealong the length of the cage from the riveting points of the supports,which are placed at regular intervals down the length of the cage. Thefilter material is preferred to touch the cage only along the edges ofthe wires, which minimizes mechanical abrasion and also allows full useof the filter material as a filtration surface.

The filter cages may be constructed as a single piece or they may bedelivered in an assembly set, to be mounted together on the locationsite with fasteners such as rivets. Long cages may be constructed in twopieces, with tubular inner joints, to be assembled during installation.

The invention as disclosed in this embodiment may be used to replacecartridge filters, with the definitive advantage of having drop-offsides that have no obstacles to catch and retain dust and pollutedparticles. The cage with the preferred top flange is reusable when thefrusto-conical, propeller-shaped fabric filter bag is replaced.

The filter bag according to the invention achieves a filtration surfacewhich is 1.5 to 2 times as large as a conventional pulse-jet filter bagof the same top diameter and length. Moreover, when the resulting filterbag is stabilized by a frusto-conical, propeller-shaped support cage 30and circular bands 12, the filter material 11 is moved more gently atlower pressure during the pulse-jet cleaning cycle. The frusto-propellershaped design has less inner-bag air volume (as in comparison toconventional cylindrical filter elements) which reduces the compressedair and energy consumption needed during the pulse-jet cleaning cycle,permitting that the frusto-propeller-shaped filter bags and cartridgescan be cleaned less aggressively in comparison to conventional pulse-jetfilter elements.

The advantages gained in using the preferred filter elements are:

lower differential pressureslower can velocityless particulate migration after pulse cyclemeeting highest emission standards due to better fine dust retentionenhanced dust-release due to propeller form, flex motion and slickdrop-off sides 43mountable frusto-conical propeller-shaped support cage 30 substantiallyfacilitates and reduces the cost of transportationThis frusto-conical propeller shaped filter bag 10 with a mouldedpropeller-shaped bottom or boot 15 according to the invention, willsubstantially lower energy cost substantially, increase the capacity andusable life span of filter elements, thereby reducing operating cost.

Thus the many aforementioned objects and advantages are most effectivelyattained. Although preferred embodiments of the invention have beendisclosed, and described in detail herein, it should be understood thatthis invention is in no sense limited thereby and its scope is to bedetermined by that of the appended claims.

LIST OF ELEMENTS NUMBERED IN THE DRAWINGS:

-   10 Frusto-conical propeller-shaped filter bag-   11 Filter cloth or filter fabric-   12 Circular band-   13 Band attachment (seam, staple and others)-   14 Ray or propeller blade-   15 Moulded propeller-shaped bottom or boot-   16 Ring cuff-   17 Snap-band cuff-   18 Top without pleats-   19 Box-pleats-   20 Frusto-conical propeller-shaped cartridge filter element-   21 Horizontal seam-   22 Inner over lap seam-   30 Frusto-conical propeller-shaped support cage-   31 Frusto-conical longitudinal wire pair-   32 Support element-   33 Ring-   34 Ray with eye-   35 Blind rivet-   36 Washer-   37 Propeller-shaped metal end piece with holes for blind rivets-   38 Top flange-   40 Propeller form-   41 Open space-   42 Mean diameter-   43 Drop-off side-   44 Top bag diameter, cell plate fit

What is claimed:
 1. A filter, comprising: an inner cage having a taperedshape from a first end of the inner cage to a second end of the innercage; a filter element that surrounds an inner cage, wherein the filterelement is held longitudinally in a frusto-conical shape by said taperedshape of said inner cage, said filter element comprising a plurality ofradially-extending members that extend from a central axis of saidfilter element and form a propeller shape in a cross-sectional view. 2.A filter as described in claim 1, said filter element further comprisinga closed and moulded, propeller shaped second end.
 3. A filter asdescribed in claim 1, said filter element further comprising apleat-free frusto-conical open first end portion.
 4. A filter asdescribed in claim 1, wherein said filter element comprises a width thatis substantially greater than a circumference of the inner shaped cage,wherein said filter element receives said frusto-conically shaped cageinto an interior of said filter element and said filter element ispositioned over said frusto-conically shaped cage.
 5. A filter asdescribed in claim 1, wherein said filter element comprises a gasketingdevice at an open first end of the filter element to facilitatereplacement of said filter.
 6. A filter as described in claim 1, whereinthe filter element comprises box-pleats at an upper, first end portionthereof, and wherein the filter element comprises filter media chosenfrom a group consisting of glass fabric, woven material, and lightweight spun-bond material.
 7. A filter as described in claim 1, whereinthe inner cage comprises a plurality of longitudinally spaced supportshaving radially outwardly extending members comprising eyelets therein,wherein said inner cage is positioned within an interior of said filterelement.
 8. A filter as described in claim 7, said inner cage furthercomprising eyelets that are fastened to a plurality of offsetlongitudinally extending frusto-conical wires, wherein said wires createa form of a propeller, and said filter element is mounted to saideyelets.
 9. A filter as described in claim 1, wherein said filterelement formed longitudinally in a frusto-conical shape comprises arigid and moulded frusto conical shaped second end, said second endcomprising a plurality of radially extending members that extend from acentral axis of said filter element and form a propeller shape in across-sectional view.
 10. A filter as described in claim 2, wherein saidmoulded, propeller-shaped second end extends from an upper portion ofsaid filter element to form a closed second end of said filter element,and said moulded, propeller-shaped second end is unitary with saidfilter element.
 11. A filter as described in claim 2, wherein saidmoulded, propeller-shaped second end extends from an upper portion ofsaid filter element to form a closed second end of said filter element,and said moulded, propeller-shaped second end is attached to said upperportion of said filter element by a generally horizontal seam.
 12. Afilter as described in claim 4, wherein said filter element is held inform relative to said inner cage by exterior annular bands attachedcircumferentially and horizontally to said filter element.
 13. A filteras described in claim 1, wherein said filter element has no pleats atany portion of an upper part of the filter element.
 14. A filter asdescribed in claim 1, wherein the filter element comprises box-pleats onan upper part of the filter element.
 15. A filter as described in claim1, wherein said filter element comprises a gasketing device at an openfirst end and mounted and fixed in a cell plate.
 16. A filter asdescribed in claim 1, wherein the inner cage comprises a plurality oflongitudinally spaced supports having radially outwardly extendingmembers, wherein said cage is positioned in the interior of said filterelement and said radially outwardly extending members support theradially extending members of the filter element.
 17. A filter asdescribed in claim 16, said inner cage comprising a plurality ofparallel and longitudinally extending, frusto-conical wires that areoffset from a center axis of the cage and are fastened to eyelets oncentral supports, wherein said wires form a propeller shape in a crosssectional view.